The present invention relates, in general, to apparatus used in the electrolytic production of metals, and more particularly, to apparatus for removing bath residue which accumulates and adheres to an electrode during production of the metal.
In the electrolytic production of a metal such as aluminum, for example, current is passed through a molten salt bath and an aluminum compound dissolved therein is reduced to yield aluminum. Typically, one of the electrodes employed in such a process is a carbon body affixed to a metal electrical conductor rod or bar which is suspended in the molten salt bath and functions as the anode. During production of the metal, solid particles of salt are placed on top of the molten salt and the carbon to prevent heat loss and prevent air burning of the carbon. The solid particles partially melt and form a hard crust of frozen salt along the surface of the molten bath and the crust adjacent the carbon body adheres thereto. Carbon is consumed in the process and the carbon body, therefore, must be replaced from time to time. To accomplish this, the metal conductor bar is detached from the current source and the used carbon body and bar assembly is lifted from the bath, and a new anode assembly is inserted into the bath.
A substantial amount of the carbon body remains on the used assembly and is referred to as the butt. The butt must be removed from the bar in order to reuse the bar, and it is also desirable to salvage the butt for making additional carbon bodies as well as salvage the frozen salt bath adhering to the butt. Before the carbon can be salvaged, the accumulation of salt bath frozen to the butt must be removed to prevent contamination of the carbon. The frozen bath may be removed by the use of manually operated pneumatic chipping hammers, but such a method is inefficient, expensive, and creates a noise and dust problem. It is proposed in Baillot et al U.S. Pat. No. 4,119,505 to mount a pneumatic hammer on apparatus which may be operated from a remote station. The apparatus is adapted to selectively move the pneumatic hammer to positions adjacent an encrusted butt and thereafter actuate the hammer against the frozen bath to break it away from the butt. Although this is an improvement over manually operating a pneumatic hammer, it does not eliminate the noise and dust problem. Other apparatus proposed for removal of the frozen crust is described in British Pat. No. 2,100,754 whereby the crust is removed by milling cutters. Use of this proposed apparatus also generates appreciable dust and noise.
It is desirable, therefore, to provide an efficient, economical method of removing frozen salt bath from an electrode and eliminate the noise and dust problem that has been attendant with methods known heretofore.